Further cleanup around DBus interface classes.

* Removed the "Glib" part from the various DbusGlib class name and added
  "Wrapper" instead: only part of the methods here declared have
  anything to do with Glib; in essence, this is an interface containing
  wrappers for various DBus functions.

* Changed "Dbus" to "DBus", to comply with the rest of the world.

* Renamed the actual implementation "RealDBusWrapper" (instead of
  "Concrete").

* Separated out RealDBusWrapper into its own header file. Client code,
  which often only cares about the abstract class, does not need to pull
  it unless specifically requiring it.

* Cleaned up the includes in these headers.

Aside from all that, also renamed system_state.cc into
real_system_state.cc, as this is what this file contains.

BUG=None
TEST=Unit tests.

Change-Id: I015c407cbc159aba8b5925eb0e916ba604c829cd
Reviewed-on: https://chromium-review.googlesource.com/189373
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
diff --git a/connection_manager_unittest.cc b/connection_manager_unittest.cc
index b8e8531..3c89cb6 100644
--- a/connection_manager_unittest.cc
+++ b/connection_manager_unittest.cc
@@ -8,7 +8,7 @@
 #include <string>
 
 #include "update_engine/connection_manager.h"
-#include "update_engine/mock_dbus_interface.h"
+#include "update_engine/mock_dbus_wrapper.h"
 #include "update_engine/mock_system_state.h"
 
 using std::set;
@@ -50,7 +50,7 @@
   DBusGProxy* kMockFlimFlamServiceProxy_;
   DBusGConnection* kMockSystemBus_;
   const char* kServicePath_;
-  MockDbusGlib dbus_iface_;
+  MockDBusWrapper dbus_iface_;
   ConnectionManager cmut_;  // ConnectionManager under test.
   MockSystemState mock_system_state_;
 };